The effect of temperature and photoperiod on the reproductive development of male and female bullfrogs will be continued. Animals reared in the laboratory will be subjected to annual cycles of temperature and photoperiod and data collected on ovary and testes changes, egg stage and changes in per cent sperm motility. The response of the reproductive system of frogs under temperature and photoperiod control to hormone injections will be determined. Behavioral studies will be undertaken to determine the effect of male-female ratios, taped choruses, confinement, and cyclic temperature and photoperiod on reproductive development and breeding behavior. Further definition of nutritional requirements of larvae will be undertaken, as will efforts to develop an artificial diet for juveniles and adults. Efforts will be continued to identify the causes of mortality due to bacterial pathogens. Disease control methods will continue on the pre- and post-metamorphic stages. BIBLIOGRAPHIC REFERENCES: Modzelewski, E.H., and D.D. Culley, Jr. 1974. Growth responses of the bullfrog, Rana catesbeiana fed various live foods, Herpetelogica. 30:397-405. Modzelewski, E.H., and D.D. Culley, Jr. 1974. Occurrence of the nematode, Eustrongylides wenrichi in laboratory reared Rana catesbeiana. Copeia, 1974:1000-1001.